Human hair becomes soiled due to its contact with the surrounding atmosphere and, to a greater extent, from sebum secreted by the head. The build-up of the sebum causes the hair to have a dirty feel and an unattractive appearance. The soiling of hair necessitates it being shampooed with frequent regularity.
Frequent shampooing causes users to want shampoo forms which are convenient to use and have pleasing aesthetics. A convenient product form for use in the shampooing process and one widely used is a "concentrate" or gel type form. These forms generally have a directionally higher surfactant level than their liquid and lotion counterparts (e.g., 21-22% vis-a-vis 15-18%). However, their gel type structure is achieved primarily through the use of a gelling or thickening polymeric material and not high surfactant levels. The use of surfactant levels greater than the 21-22% level is desirable to achieve greater cleaning power.
A pleasing aesthetic attribute desired by many users in their shampoo is for it to be clear (i.e., isotropic). Achieving an isotropic composition with a surfactant concentration in the 24-40% range and higher is something that is desirable for the reasons given above but not easily achieved.
Many references disclose compositions which contain high levels of surfactant but not all claim to be isotropic and many probably do not represent compositions which had actually been prepared. Among such references is Japanese Published Application J No. 60141797, July 26, 1985 disclosing a gel composition comprising an ethoxylated alkyl sulfate and a betaine. Other references have similar disclosures. Japanese Published Application J No. 6163-198, December 15, 1981 discloses mixtures of anionic sulfate surfactants and betaine surfactants. U.S. Pat. No. 3,980,769, Sept. 14, 1976 to Ghilardi et al. discloses detergent composition containing a mixture of anionic and amphoteric surfactants. U.S. Pat. No. 4,110,263, Aug. 29, 1978 to Lindemann et al. discloses cleaning compositions containing anionic and amphoteric surfactants. U.S. Pat. No. 4,246,131, Jan. 20, 1981 to Lohr discloses water free surfactant compositions comprising a mixture of betaine and alkyl sulfate surfactants wherein the surfactants comprise at least 40% of the compositions. U.S. Pat. No. 4,329,334, May 11, 1982 to Su et al. discloses shampoo compositions which contain a mixture of anionic and amphoteric surfactants.
While the prior art, such as that discussed above, discloses compositions containing high surfactant levels, there still is the need for compositions containing not only high surfactant levels but which also are isotropic.
The present inventor has surprisingly found that such compositions can be prepared by combining alkyl sulfate or sulfonate surfactants with betaine and sarcosinate surfactants.
It is an object, therefore, of the present invention to provide compositions which contain high levels of surfactant.
It is a further object of the present invention to provide such compositions which are isotropic.
It is a further object of the present invention to provide such compositions which have sufficient viscosity to be a gel or concentrate.
It is still a further object of the present invention to provide such compositions which lather well and clean well.
These and other objectives will become readily apparent from the detailed description which follows.
All percentages and ratios herein are by weight unless otherwise specified.